1. Technical Field
The present invention relates to a power supply voltage detection circuit for detecting the magnitude of a power supply voltage. Furthermore, the invention relates to a semiconductor integrated circuit device incorporating such a power supply voltage detection circuit, an electronic device using such a semiconductor integrated circuit device, and the like.
2. Related Art
For example, in an electronic device that operates with a power supply voltage supplied from a battery, the power supply voltage supplied from the battery is supplied to a number of circuit blocks after being stabilized by a regulator. Generally, power supply voltage detection circuits outputs a signal representing a comparison result, by comparing the power supply voltage that is output from the regulator with a predetermined voltage.
As related technology, JP-A-11-119870 (paras. 0005-0006; FIG. 1) discloses a power supply voltage detection circuit configured to enable a user to more reliably check when to replace the battery of a mobile electronic device than was previously possible. This power supply voltage detection circuit is provided with a first detection circuit for detecting a first voltage that is higher than a minimum voltage guaranteeing normal operation of the electronic device, a second detection circuit for detecting a second voltage between the first voltage and the minimum voltage, a first flag circuit that is set when the first detection circuit detects a state where the power supply voltage has dropped to the first voltage, a second flag circuit that is set when the second detection circuit detects a state where the power supply voltage has dropped to the second voltage, and an interrupt processing circuit to which the output of the first and second flag circuits is supplied and prioritizes execution of interrupt processing in accordance with the state of the first flag circuit over interrupt processing in accordance with the state of the second flag circuit, and the power supply voltage detection circuit output a signal for warning that the power supply voltage has dropped to near the minimum voltage, by performing interrupt processing in accordance with the state of the first flag circuit, when the power supply voltage drops to the first voltage.
The power supply voltage detection circuit of JP-A-11-119870 also conceivably detects the magnitude of the power supply voltage that is output from the regulator. However, in the case of wanting to know the remaining capacity of the battery in order to estimate when to replace or charge the battery, the remaining capacity of the battery can be more accurately known by detecting the magnitude of the power supply voltage that is supplied from the battery rather than by detecting the magnitude of the power supply voltage that is output from the regulator. Also, in the case of using an electronic switch in order to select one power supply potential from among a plurality of power supply potentials, inflow of current from nodes to which a power supply potential that has not been selected is supplied is a problem.